2 is a factor and r is a factor so the equation becomes
2r(r^2 + 4r + 3)
then we can factor the term in parentheses. To do that, we know the first term in each set of parentheses must be r and r. Then we look for the last term something which multiplied together gives 3 but added together gives 4. The factors of 3 are 3 and 1, so
2r(r + 3)(r + 1). I hope this helps.